
To evaluate the influences of nitrogen levels and weed density on growth indices of wheat a two years field experiment was conducted at Research Field of Islamic Azad University of Ahvaz-Iran in 2007-8 and 2008-9 cropping season. The results showed that increasing nitrogen application from 90 to 210 kg N ha-1 increased the negative interference effects of wild mustard and wild oat on Total Dry Matter (TDM), Leaf Area Index (LAI) and Crop Growth Rate (CGR). Inter specific competition of wild mustard and wild oat significantly decreased the plant height, TDM, LAI and CGR and maximum values were noted in zero density of wild mustard and wild oat. Among the nitrogen levels the highest TDM, LAI and CGR was observed in the application of 150 kg N ha-1.